1. Field of the Invention
The present invention relates to a protective tape used for optical member. Furthermore, it relates to a treated layer forming agent used for protective tape used for optical member. The protective tape used for optical member of the invention is used for protection of a surface of various optical films, such as polarizing plates and retardation plates. The protective tape is used for protection of liquid crystal displays to attach on a surface of a liquid crystal display panel, and is used for protection of various kinds of image viewing displays, such as organic electroluminescence displays, PDPs, and etc.
2. Prior Art
Protective tape used for optical member has plastic film bases, such as polyethylene terephthalate and polyethylene, and have adhesive layers applied to the base. The protective tape used for optical member is attached on materials to be protected via an adhesive layer, and protects the materials to be protected from blemish, contamination, etc. For example, as optical materials to be protected, optical films, such as polarizing plates and retardation plates, may be mentioned (Japanese Patent Publication No. Hei 4-30120).
The above-mentioned protective tape protects one side of the optical film during various manufacturing processes. On the other hand, adhesive layer, such as acrylic based adhesive, is formed onto an opposite side of the optical film. Furthermore, the adhesive layer is covered with a release liner. Subsequently, the optical film with the protective tape is cut and processed according to a size of a liquid crystal cell. In addition, printing in ink is given to a backside (opposite side of the adhesive layer of the protective tape) of a base of the above-mentioned protective tape in order to enable distinction for various intended uses. And the optical film with protective tape is piled up, and stored.
Then, after various production processes or inspection, a release liner of the optical film with the protective tape is released, and, subsequently the optical film is attached to a liquid crystal cell. Then, the above-mentioned protective tape is released and is removed in a stage where protection of a surface for an optical film is not required, for example, a state immediately before a liquid crystal panel is built into a personal computer.
As a method of releasing a protective tape, a method may be often adopted in which a commercially available cellophane adhesive tape is attached on a corner of a protective tape, then the tape is vertically pulled up, and thereby the surface protective tape is released together with the tape (Japanese Patent Publication No.hei 9-113726). This is because that this method has a large effect of preventing damage or releasing in a corner of an optical film in comparison with a method of directly releasing protective tape by hand.
In the optical film with the above-mentioned protective tape, when they are piled up after cutting processing, there is a possibility that adhesives over flown from a cut surface may adhere to the surrounding protective tapes. Therefore, a treated layer (antifouling layer) comprising releasing agent etc. is formed on a backside of the protective tape base so that blocking of the optical film with the protective tape may not given. And as treat agent, a polymer containing long chain alkyl group, silicone type or fluoride type release agent is proposed (for example, Japanese Patent Publication No.hei 11-256115, Japanese Patent Publication No.hei 11-256116).
However, a treated layer formed on the backside makes difficult direct printing onto the treated layer by ink for discrimination of intended uses, using treat agent indicated by the above-mentioned Referential Patents. In conventional methods, by such reason, a portion to be printed in the treated layer was once wiped off with solvents, such as toluene, to make the portion clean, and then printing was given to an exposure plastics surface. On the other hand, if the treated layer is designed so that a direct printing to the treated layer may be enabled, inevitably, the treated layer concerned will have good adhesive property with adhesives over flown from a cut surface, as a result, leading to occurrence of blocking.